The invention relates to ophthalmic lenses. In particular, the invention provides lenses that use a progressive cylinder power.
Astigmatism, caused by either an unequal radius of curvature of the cornea in all directions or unequal bending of light by the crystalline lens, is a common refractive error. The result of astigmatism is that the eye cannot focus rays of light on the retina because the rays are not refracted equally in all directions. To correct astigmatism, it is common to incorporate cylinder correction of a specific power and axis in the astigmatic individual""s ophthalmic lens.
Typically, the cylinder power for a lens is fixed. However, a multifocal lens in which the cylinder power is different for areas of different refractive power is known, as for example in U.S. Pat. No. 6,142,625. The lens of U.S. Pat. No. 6,142,625 is disadvantageous in that there would be image jump in the lens resulting from the difference in power, axis, or both between adjacent areas of the lens. Therefore, a need exists for a variable cylinder lens which overcomes this disadavantage.